The problem of accidental separation of connected electrical cords at the mating connection between the cords, for example, at the mating connection between a pigtail electrical cord extending from a power tool or an electrical appliance and an extension cord, is a common one particularly as the power tool or appliance is operated and tension is applied to the interface between the pigtail cord and the extension cord such as when the tool or appliance is moved by the operator in a direction away from the electrical outlet into which the extension cord is inserted.
As such, several prior art devices have been disclosed to reduce the instances of the above-described electrical cord separation. U.S. Pat. No. 2,461,427 to Kneebone discloses an elongate member having a hook defining a space at one end and including an opening at the other end. The member is sized so that when the plug and socket head on the ends of the electrical cords are attached to one another with the cords extending through the space and opening respectively, the member is resiliently deformed into an arc to frictionally engage the hook and the edges of the opening against the respective cords. Over time, such resilient deformation can cause the member to fatigue reducing the frictional force engaging the cords and/or causing the member to fail.
U.S. Pat. No. 3,781,761 to Harwood discloses a strip of material having a series of apertures spaced along the strip opening to a side of the strip for receipt of a pair of cords each through at least one aperture. Tension applied to a cord will be absorbed by the strip as by slight flexure thereof. Similar to the device disclosed by Kneebone, the strip is subject to fatigue by the flexure caused by repeated use and application of tension to cords therein. Further, the apertures are open to the side of the strip such that any force applied to the cord in the direction of the strip side can cause the cords to become dislodged from the strip.
U.S. Pat. No. 4,183,603 to Donarummo discloses a cord lock having a U-shaped body with parallel end legs having cord-receiving apertures therein with the male plug and female socket of the respective cords being connected between the legs. The cords are prevented from separation by being captured tightly between the end legs such that any tension applied to a cord causes the plug or socket head to abut the adjacent end leg before detaching from the other cord. Thus, the distance between end legs must be selected so that the distance is only slightly greater than the length of the connected plug and socket therebetween so that for any variations in the length of the connected plug and socket a different U-shaped body must be provided.
U.S. Pat. No. 4,773,874 to Kopeski, Jr. discloses a U-shaped clip having end portions on the legs which are curled over towards the bottom of the clip. The end legs have slots leading to respective openings for receipt of cords therethrough allowing plug and socket heads to be connected between the end legs. With such a connection, the curled over portions of the end legs engage the top of the heads and force them downwardly towards the bottom of the clip. Again, such flexure of the clip, and specifically the curled-over end portions, subject the clip to fatigue and possible failure upon repeated usage thereof. Moreover, similar to the device disclosed by Donarummo, the clip is designed such that the plug and socket heads fit closely between the end legs such that plug and socket heads of varying lengths would require a differently sized clip.
U.S. Pat. No. 4,957,450 to Pioszak discloses a strap which is wrapped around connected plug and socket heads and then connected to itself by a Velcro hook and loop fastening system. Such a fastening system can be a problem when used outdoors as the hooks and loops employed therein can become clogged with ice and snow or dirt and the like and lose their fastening ability. In another embodiment, the strap is attached directly to the bottom of the male plug and is wrapped around the female socket head connected to the male plug and attached to the top of the male plug head. The male plug head is custom-made with posts on the top of the male plug and the strap is provided with a series of holes which can be aligned with the posts to connect the strap to the top of the male plug. The use of specially-made plug heads having posts increases manufacturing costs, and accordingly is not desirable.
U.S. Pat. No. 5,336,106 to Osten discloses a connector having flexible thumb tabs which allow cords to be inserted into openings at either end of the connector. Again, similar to other devices using flexible members, the flexible thumb tabs are subject to failure upon repeated usage.